Xchat is a very well-known IRC client because it is compatible with most operating systems. It includes all standard options, you can select the server, color, menu with the basic commands, etc… Moreover, it has friendly functions like the possibility to connect to several servers.
You can also edit very easily most menus in order to personalize your chat space. The software is free for most operating systems. The tool is light, pleasant to use and can be used in graphic or console mode. It is not necessary any more to install GTK graphic library + Runtime Environment for Windows users because they are included in the installer since version 2.6.